[support] Two Sites - Different Current Core Versions

[ Ubuntu 12.04.4 ] I received an email about updating core on one of my sites. That was done, showing that Drupal core was updated from 7.27 --> 7.28. I then went to another of my sites and (doing the usual) ran Drush (drush update). It show the version at *7.27* with no need to update! Using "admin/reports/updates", however, shows that 7.28 *is* available. I flushed all caches on the second site with no difference. Drush still isn't showing an available 7.28 update. Ideas? -- Prof Kenneth H Jacker khj@cs.appstate.edu Computer Science Dept www.cs.appstate.edu/~khj Appalachian State Univ Boone, NC 28608 USA